My thoughts on "top" girl or boy.
For a boy to be "top", he needs to be able to sit in yeshiva, capable of learning, and while he's there, daven with a minyan. And if he's really special, he has good midos too.
For a girl to be "top" she's got to have good looks and midos.
So it's easier to be a top girl than a top boy.
Then the Bais Yakov system ranks full time learning as the model for a top boy. So she's only looking for a top boy.
So it makes the numbers game worse.